Naiveté, Projection Bias, and Habit Formation in Gym Attendance
通过健身房出勤激励实验，发现参与者高估未来出勤（天真），且干预后出勤增加（习惯形成）但未被提前预测，这可用投射偏差解释，并有助于理解动态不一致者为何少用承诺机制。
We implement a gym-attendance incentive intervention and elicit subjects' predictions of their postintervention attendance. We find that subjects greatly overpredict future attendance, which we interpret as evidence of partial naiveté with respect to present bias. We find a significant postintervention attendance increase, which we interpret as habit formation, and which subjects appear not to predict ex ante. These results are consistent with a model of projection bias with respect to habit formation. Neither the intervention incentives, nor the small posttreatment incentives involved in our elicitation mechanism, appear to crowd out existing intrinsic motivation. The combination of naiveté and projection bias in gym attendance can help to explain limited take-up of commitment devices by dynamically inconsistent agents, and points to new forms of contracts. Alternative explanations of our results are discussed. Data, as supplemental material, are available at http://dx.doi.org/10.1287/mnsc.2014.2091 . This paper was accepted by Uri Gneezy, behavioral economics.